全文获取类型
收费全文 | 68448篇 |
免费 | 6874篇 |
国内免费 | 3642篇 |
专业分类
电工技术 | 12260篇 |
技术理论 | 7篇 |
综合类 | 5567篇 |
化学工业 | 7230篇 |
金属工艺 | 3988篇 |
机械仪表 | 4842篇 |
建筑科学 | 4249篇 |
矿业工程 | 2794篇 |
能源动力 | 3483篇 |
轻工业 | 2897篇 |
水利工程 | 2592篇 |
石油天然气 | 4963篇 |
武器工业 | 722篇 |
无线电 | 7351篇 |
一般工业技术 | 4397篇 |
冶金工业 | 4842篇 |
原子能技术 | 626篇 |
自动化技术 | 6154篇 |
出版年
2024年 | 325篇 |
2023年 | 861篇 |
2022年 | 1710篇 |
2021年 | 1944篇 |
2020年 | 2210篇 |
2019年 | 1699篇 |
2018年 | 1713篇 |
2017年 | 2096篇 |
2016年 | 2458篇 |
2015年 | 2644篇 |
2014年 | 4516篇 |
2013年 | 3829篇 |
2012年 | 5558篇 |
2011年 | 5666篇 |
2010年 | 4050篇 |
2009年 | 3868篇 |
2008年 | 3518篇 |
2007年 | 4559篇 |
2006年 | 4211篇 |
2005年 | 3618篇 |
2004年 | 2866篇 |
2003年 | 2763篇 |
2002年 | 2295篇 |
2001年 | 2110篇 |
2000年 | 1745篇 |
1999年 | 1354篇 |
1998年 | 923篇 |
1997年 | 786篇 |
1996年 | 678篇 |
1995年 | 541篇 |
1994年 | 447篇 |
1993年 | 272篇 |
1992年 | 244篇 |
1991年 | 195篇 |
1990年 | 157篇 |
1989年 | 136篇 |
1988年 | 89篇 |
1987年 | 60篇 |
1986年 | 39篇 |
1985年 | 46篇 |
1984年 | 35篇 |
1983年 | 25篇 |
1982年 | 11篇 |
1981年 | 13篇 |
1980年 | 15篇 |
1978年 | 7篇 |
1975年 | 5篇 |
1964年 | 5篇 |
1962年 | 5篇 |
1959年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
Significant increases in the activity of vanadium(III) amidinate catalysts for ethylene polymerization have been obtained by immobilization on a MgCl2‐based support prepared by reaction of AlEt3 with a MgCl2/ethanol adduct. Catalyst immobilization and activation on this type of support prevents the rapid decay in activity observed under homogeneous polymerization conditions with unsupported catalysts. Stable polymerization activity is also observed with analogous titanium(III) complexes. Polyethylene with narrow molecular weight distribution and spherical particle morphology is obtained without reactor fouling. Copyright © 2005 Society of Chemical Industry 相似文献
32.
RRN Sailaja 《Polymer International》2005,54(12):1589-1598
Lignin was graft copolymerized with methyl methacrylate using manganic pyrophosphate as initiator. This modified lignin was then blended (up to 50 wt%) with low density polyethylene (LDPE) using a small quantity of poly[ethylene‐co‐(glycidyl methacrylate)] (PEGMA) compatibilizer. The mechanical properties of the blend were substantially improved by using modified lignin in contrast to untreated lignin. Differential scanning calorimetry studies showed loss of crystallinity of the LDPE phase owing to the interaction between the blend components. Thermogravimetric analysis showed higher thermal stability of modified lignin in the domain of blend processing. This suggested that there is scope for useful utilization of lignin, which could also lead to the development of eco‐friendly products. Copyright © 2005 Society of Chemical Industry 相似文献
33.
34.
35.
Why are human observers particularly sensitive to human movement? Seven experiments examined the roles of visual experience and motor processes in human movement perception by comparing visual sensitivities to point-light displays of familiar, unusual, and impossible gaits across gait-speed and identity discrimination tasks. In both tasks, visual sensitivity to physically possible gaits was superior to visual sensitivity to physically impossible gaits, supporting perception-action coupling theories of human movement perception. Visual experience influenced walker-identity perception but not gait-speed discrimination. Thus, both motor experience and visual experience define visual sensitivity to human movement. An ecological perspective can be used to define the conditions necessary for experience-dependent sensitivity to human movement. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
36.
37.
在Booth算法的基础上,结合MIPS 4KC微处理器中的流水线结构和乘法器的工作过程,提出了一种改进的Booth乘法器的设计方法,并采用全制定方法实现,用这种方法实现的乘法器单元具有面积小、单元电路可重复性好、版图设计工作量小、功耗低等特点. 相似文献
38.
Sangkwon Jeong 《低温学》2004,44(4):241-248
This paper describes transient numerical modeling for thermal characteristic of vapor-cooled current leads under pulse operation. The transient thermal analysis considers the temperature difference between a helium gas flow and a copper lead with temperature dependent properties of helium gas, copper and stainless steel. The numerical analysis was validated by an experiment with commercially available 100 A vapor-cooled current leads. A proper overloading factor calculation and the effect of intermediate cooling are presented for the current leads under pulse operation, which can significantly reduce heat input to a cryostat. 相似文献
39.
Yun‐Hwei Shen 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(5):581-586
A novel strategy of sweep coagulation to treat low turbidity water is presented herein. Study findings demonstrated that an Na+‐saturated bentonite with medium cation exchange capacity (CEC) resulted in significant turbidity removal at a bentonite dosage of 30 mg dm?3. Bentonite dispersion with fully delaminated platelets tended to undergo a more porous type of coagulation with intense face‐to‐face interactions of platelets and effectively entrapped TiO2 particles in band‐type structures. This type of coagulation usually results in a large volume of settled flocs with a fluffy structure and excellent turbidity removal efficiency for sweep coagulation. The sign and magnitude of electrical charge on TiO2 particles has a minor effect on the efficiency of sweep coagulation. Copyright © 2005 Society of Chemical Industry 相似文献
40.
SLIMLINE K型多功能撬装双滚筒试井绞车为整体式结构,多用于海上平台,可进行电子压力计和机械压力计试井,以及井下工具的投放、震击、打捞等完井作业。该试井绞车采用先进的数控技术,使起下纲丝/电缆实现自动化控制,该系统能够对斜井、定向井进行随钻测试。 相似文献